hard milled means that there is less air beaten into the mix- the opposite of Ivory soap, which is beaten 'fluffy with air, much like soft-serve ice cream. and any hard milled soap is going to last longer than a softer soap.

beyond that- it's all marketting. their soap's no better than Yardely's of London, who at least doesn't make a fuss about their lavendar soap being 'organic' just because they're using real lavendar from plants!